There is no problem with a pre-mine, as long as the address is transparent and the bounties are rewarded to encourage growth. Because of the way most alt-coins explain their pre-mines, people just assume they are kept by the devs ready for a dump when it hits an exchange. This can be true, but if the pre-mine is transparent and all of the paid bounties can be seen, then the infrastructure of the coin is developed by the community thus increasing the coins value. Its a win-win situation.

One coin that has adopted this method and impressed me with their transparency is DigiByte - http://digibyte.co/pre-mine-accounts